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High-strength polyurethane adhesive

a polyurethane adhesive, high-strength technology, applied in the direction of adhesive types, layered products, chemistry apparatus and processes, etc., can solve the problems of short molding time of two component adhesives based on pu that cannot be achieved with one component polyurethane adhesives, and long molding time of 1k pu adhesives, etc., to achieve the effect of long processing tim

Inactive Publication Date: 2009-10-29
HENKEL KGAA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007]Accordingly, the object of the invention was to provide a method permitting a simple application of a one component polyurethane adhesive having a long processing time and that can make up for possible unevenness of the substrate surface on bonding.
[0008]According to the invention, the object is achieved by referring to the claims. It concerns the provision of a method, in which a moisture curing 1K polyurethane adhesive is applied at a low temperature and which has only a low reactivity during and after its application. The coated substrate can optionally be stored; after the bonding and pressing with a second substrate and a crosslinking at increased temperature, there then results a high-strength adhesive bond. The adhesive foams slightly during the crosslinking reaction, thereby enabling the height differences between the substrate surfaces to be equalized and a smooth surface to be obtained.

Problems solved by technology

2K PU adhesives of this type require an exact dosing of the ingredients and have only a limited processing time.
In general, the short molding times of two component adhesives based on PU are not achieved with one component polyurethane adhesives.
1K PU adhesives often react very slowly and require a lengthy molding time.
Moreover, these adhesives are moisture-sensitive, even to air humidity, and consequently are only storage stable for a short time after application.
A further disadvantage of the known adhesives is that they are generally applied in a thin layer in order to ensure a good adhesion.
If the substrates have distinctly uneven surfaces, then the adhesive just cannot fill these spaces.
With rigid substrates, there remain cavities that weaken the strength of the adhesive bond.
In contrast, if greater amounts of the adhesive are applied then the problem arises that the excess adhesive has to be leveled and possibly leaks out of the sides of the adhesive bond.
This causes contamination of the bonded object or of the equipment used.
Apart from that, the cohesion of thick adhesive layers—particularly for foamed glued joints—is often poor.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0053]10 parts of a polyether diol based on propylene glycol with an Mn of ca. 2000 were dried under vacuum. To this diol were added a further 30 parts of an oleochemical polyol with an Mn of ca. 1000 and an OH number of ca. 200. To this mixture were added 60 parts of crude MDI (Isonate 143 L). The mixture was homogenized and stirred at a temperature of 75° C. for 30 minutes. An adhesive was obtained with a NCO content of 16% and a viscosity of 10,000 mPas at 30° C.

example 2

[0054]39.5 parts of an oleochemical polyol with an Mn of 1000 and an OH number of 200 were freed from water under a vacuum. 0.5 parts of pentaerythritol were added. To this mixture were added 60 parts of crude MDI. 0.01% DBTL were added as catalyst, the mixture was homogenized and allowed to react for one hour at 50° C. An adhesive was obtained with a viscosity of 50,000 mPas at 30 ° C. and an isocyanate content of 17%.

example 3

[0055]25 parts of an oleochemical polyol with an Mn of ca. 1000 and an OH number of ca. 200 were dried. To this mixture were added 75 parts of crude MDI (Isonate 143 L). The mixture was homogenized and stirred at a temperature of 75° C. for 30 minutes. An adhesive was obtained with a NCO content of 20% and a viscosity of 20,000 mPas at 30° C.

Adhesive Bonding:

[0056]1) A beech wood object was cleaned to remove adherent dust constituents. An adhesive according to examples 1 to 3 was then applied with a coating layer of ca. 50 μm with a knife blade at room temperature (25° C.). After cooling the substrate, a storage stable coating was obtained. An aluminum test piece was coated in the same way.

[0057]The coated substrates were adhesively bonded with a corresponding substrate. The adhesively bonded substrates were then subjected to a pressure of 10-100 kg / m2 in a press, the work piece being simultaneously heated to 150° C. The pressure and temperature were maintained for 10 minutes.

[0058]...

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Abstract

The invention relates to a method for adhesively bonding substrates together that contains irregularities on the surface of the substrates. The adhesive is particularly suitable for adhesively bonding thin flexible substrates onto a rigid substrates.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of PCT / EP2007 / 059626 filed Sep. 13, 2007, which claims the benefit of DE 10 2006 054 197.9, filed Nov. 15, 2006, the complete disclosures of which are hereby incorporated by reference in their entirety.FIELD OF INVENTION[0002]The invention relates to a method for adhesively bonding wood materials, wherein a 1K polyurethane adhesive is applied onto a substrate half and is then adhesively bonded by pressing against the second substrate, wherein an activation occurs by increased temperature during the bonding. A high initial adhesion is achieved and the adhesive increases in volume such that irregularities on the substrate sides facing one another are leveled out and a smooth surface is obtained.BACKGROUND[0003]Two component polyurethane adhesives are described in EP 1 366 132 which describe / comprise 10 to 98% of an oleochemical polyol, 1 to 7.5% of a diol having an OH number from 400 to 2000, 1 to 7.5% of ...

Claims

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Application Information

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IPC IPC(8): B32B37/12C08L75/04
CPCC08G18/12C08G18/36C08G18/6696C09J175/04C08G18/307
Inventor GARMANN, HELGAPUCK, CLAUS-HEINRICHMOSSHAMMER, GERHARD
Owner HENKEL KGAA
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